Browsing by Author "Foulds, Gary André"

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    Spectroscopic studies of Metal(II) complexes and application of the Ni(II) complexes to olefin oligomerisation catalysis
    (1990) Bennett, Alison Margaret Anne; Thornton, David A; Foulds, Gary André
    Complexes of some divalent first row transition metal ions with various ligands have been prepared. These included bis-complexes of β-ketoenolate ligands, nickel complexes of trialkylphosphine and nickel complexes containing phosphine and β-ketoenolate ligands, and finally, tris, bis and mono(ethylenediamine) complexes. Composition was ascertained by microanalysis and ¹H, ¹³C NMR of the diamagnetic complexes. In addition, the crystal structure of one of the nickel β-ketoenolate triethylphosphine complexes was determined. The infrared spectra of the above compounds have been examined over the range 4000-50 cm⁻¹ with a view to determining band assignments based on metal ion substitution, ligand substitution (for phosphine and β-ketoenolate complexes), ligand and metal ion isotopic labelling [for tris(ethylenediamine) complexes] and anion substitution (for phosphine and ethylenediamine complexes). In each case, spectra-structure correlations have been established and are discussed. Each of the nickel complexes prepared above was tested as a catalyst for the oligomerisation of 1-hexene. The experiments were carried out in batch at 40°C using toluene as solvent. Four different Lewis acid cocatalysts were tested and nickel : co-catalyst ratios of 1:1 and 1:10 were used. The effects of Lewis acid strength and concentration, nickel complex structure, a change in the donor chelating atom and the presence of phosphine ligands on the isomerisation, as well as the activity and selectivity of the oligomerisation reaction, are discussed. Two polymer-supported catalyst complexes have been prepared; the first,: by polymerisation of a nickel β-ketoenolate complex monomer and th, second, by binding a nickel β-ketoenolate phosphine complex to a polystyrene support through the phosphine ligand. The resultinJ polymers were extensively characterised by microanalysis, infrared, ¹H and ¹³C NMR, mass spectrometry, energy dispersive X-ray and thermal techniques. In the presence of a ten-fold excess of the ethylaluminium dichloride co-catalyst, each supported complex formed an active 1-hexene oligomerisation and isomerisation system. The activity and selectivity of each system have been compared to that of their respective monomers. Finally, the polymerised ,8-ketoenolate monomer was tested at various temperatures as a propene oligomerisation catalyst and the effect of temperature on activity and selectivity is discussed.
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    A spectroscopic study of square planar platinum (2) complexes
    (1983) Hall, Philip Simon; Thornton, David A; Foulds, Gary André
    A number of spectroscopic techniques consisting of ultraviolet, ¹H-NMR and mass spectrometry have been used in the structural analysis of square planar Pt(II) complexes. The complexes trans-[PtBr₂(Y) (R-an)] (Y = C₂H₄,CO; R-an = substituted aniline) were prepared and investigated by the spectrosopic techniques. Infrared assignments were aided by isotopic labelling studies. The discussion of the two series of complexes are based on their relation to one another. The complexes trans-[PtX₂ (CO) (L)] (X = Cl, Br; L = aniline, pyridine N-oxide, pyridine, ammonia, imidazole and pyrazole) were prepared from their corresponding ethylene analogues. Infrared assignments, with labelling studies, are given for the complexes. The bonding effects in these complexes were studied using ¹H-NMR and ultraviolet spectroscopy. The ¹H-NMR spectra reveal that there is a fluxional behaviour of the ligands in some of the complexes. Hence, cold temperature studies were required to "freeze out" this fluxional behaviour and observe the expected signals due to the ¹⁹⁵pt-H coupling. The electronic effects are different when the ligand, L, was capable of forming σ-bonds with Pt²+, compared to when L was capable of forming both a- and π-bonds with Pt²+. The mass spectra show the M+ peak and subsequent fragmentation in the complexes. The fluxional behaviour of imidazole in trans-[PtX₂(C₂H₄) (Him)] was monitored by cold temperature studies. Using band shape analysis (with the aid of a computer) the activation paramaters for the exchange processes were determined. The dependence of the imidazole proton signals on temperature, solvent and excess ligand, all indicate that an intermolecular exchange process is occurring. Studies on the complex trans-[PtX₂(C₂H₄) (pyz)] and the effect of solvent on the complexes are being pursued, and it is hoped that an understanding of the role of the solvent in the exchange process will become apparent.
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    A spectroscopic study of square planar platinum (II) complexes
    (1982) Foulds, Gary André; Thornton, David A
    A number of spectroscopic techniques consisting of infrared, Raman ultraviolet and 1H-nmr spectroscopy have been used in the structural analysis of square planar Pt(II) complexes.